Status of the aces project: Space instruments performance and ground segment organization

The ACES project aims at operating ultra stable clocks on board the International Space Station ISS and comparing them to ground clocks located all around the world. The expected performance of ACES space clocks (frequency stability and accuracy at 10 ^-16 level) and of the dedicated microwave link (time stability better than 10 ps over 1 day) will be of great interest for time & frequency metrology (comparison of ground primary standards with a resolution better than 10 ^-16) and for fundamental physics (relativity tests).